US6407935B1 - High frequency electronic ballast with reactive power compensation - Google Patents
High frequency electronic ballast with reactive power compensation Download PDFInfo
- Publication number
- US6407935B1 US6407935B1 US09/580,170 US58017000A US6407935B1 US 6407935 B1 US6407935 B1 US 6407935B1 US 58017000 A US58017000 A US 58017000A US 6407935 B1 US6407935 B1 US 6407935B1
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- United States
- Prior art keywords
- transformer
- circuit
- voltage
- current
- lamp
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- 239000003990 capacitor Substances 0.000 claims abstract description 37
- 238000004804 winding Methods 0.000 claims abstract description 34
- 238000000034 method Methods 0.000 claims 9
- 230000008878 coupling Effects 0.000 claims 7
- 238000010168 coupling process Methods 0.000 claims 7
- 238000005859 coupling reaction Methods 0.000 claims 7
- 238000010586 diagram Methods 0.000 description 10
- 239000013598 vector Substances 0.000 description 10
- 230000000903 blocking effect Effects 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 230000010363 phase shift Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5383—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a self-oscillating arrangement
- H02M7/53832—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a self-oscillating arrangement in a push-pull arrangement
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
- H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
- H05B41/282—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices
- H05B41/2825—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices by means of a bridge converter in the final stage
- H05B41/2827—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices by means of a bridge converter in the final stage using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations
Definitions
- the present invention is directed to a lamp ballast circuit, and more particularly to a ballast circuit wherein the magnetizing inductance of the output transformer is adjusted in order to compensate for the reactive power induced by a ballast capacitor.
- Fluorescent lighting is a very common type of illumination. Fluorescent lamps function when an electrical arc is established between two electrodes located at opposite ends of the lamp. The electrical arc is established by supplying a proper voltage and current to the lamp. The lamp is filled with an ionizable gas and a very small amount of vaporized mercury. When the arc is established, collisions occur between the electrons and the mercury atoms, causing the emission of ultraviolet energy.
- the fluorescent lamps have a phosphorous coating on their inner surface, which transforms the ultraviolet energy into diffused, visible light.
- a high voltage is typically required. However, once the lamp has been turned on, a lesser voltage is required to maintain the lamp's operation.
- a fluorescent lamp ballast is used. Among other functions (such as limiting the current flow through the lamp once it has already been started), a ballast is a device which provides the appropriate voltage to establish the arc through the lamps.
- FIG. 1 shows a schematic diagram of a prior art ballast circuit 100 which employs a DC supply source 150 .
- the DC supply source 150 is coupled to a pair of enhancement mode n-channel MOSFET transistors 102 and 104 , which form a half-bridge structure. When alternately turned “on” and “off”, transistors 102 and 104 provide an AC voltage signal to the lamps.
- the drain terminal of transistor 102 and the source terminal of transistor 104 are connected at node 106 .
- Node 106 is further coupled to current blocking capacitor 114 and resonant inductor 112 , which are coupled in series. Current blocking capacitor 114 prevents DC current from flowing through the lamps.
- Resonant inductor 112 is further coupled to a primary winding 110 a of transformer 110 .
- Resonant capacitor 116 is coupled in parallel across primary winding 110 a .
- Secondary winding 110 b of transformer 110 is coupled to a series combination of capacitors 122 , 124 , 126 and 128 and fluorescent lamps 132 , 134 , 136 and 138 coupled together in parallel.
- Capacitors 122 , 124 , 126 and 128 control the current flow through lamps 132 , 134 , 136 and 138 , respectively.
- the power transferred through transformer 110 to drive the lamps is comprised of both a real power component (i.e.—the power provided to the lamps) and a reactive power component, which is described below.
- Reactive power exists in a circuit due to an imbalance between peak magnetic energy storage and the peak electric energy storage in a circuit.
- the capacitor in the circuit stores its maximum energy when the voltage is maximum.
- the inductor stores its maximum energy when its current is maximum, which occurs when the voltage is zero because of the 90 degree phase shift. Since the ballasting capacitors 122 , 124 , 126 and 128 and the lamp load require energy at different times in the AC cycle, additional energy must periodically be supplied by the circuit in order to balance the load (i.e.—the lamps). This energy, transferred in and out of ballasting capacitors 122 , 124 , 126 and 128 during each cycle, is the reactive power.
- transformer 110 Because of the additional reactive power that is not transferred to the load itself, prior art circuits are configured with a transformer that is large enough to handle the additional reactive power. In the case of the circuit described in FIG. 1, the reactive power is transferred by transformer 110 . In order to insure that the reactive power is always sufficient to balance the load, transformer 110 must be sized significantly larger than if it was not required to transfer reactive power. The overdesign of this transformer undesirably adds to the cost and to the physical size of the lamp ballast circuit.
- the present invention is directed to a lamp ballast circuit with an adjusted magnetizing inductance of the lamp ballast circuit transformer.
- the magnetizing inductance of the transformer By optimizing the magnetizing inductance of the transformer, the voltage and current signals received at the primary side of the transformer are brought in phase relative to each other, and the reactive power transferred by the transformer is substantially reduced or eliminated. Since the transformer is not required to transfer reactive power, it may be sized significantly smaller, thereby decreasing the cost and the physical size of the lamp ballast circuit.
- the lamp ballast circuit comprises a DC voltage and current supply source.
- a pair of transistors is coupled to the DC supply source and is configured, upon application of the DC signal, to provide an AC voltage and current signal, wherein each of the AC voltage and current signals has a corresponding phase.
- a transformer includes a primary and a secondary winding, wherein the primary winding of the transformer receives the AC voltage and current signals.
- At least one lamp is coupled to the secondary winding via a capacitor.
- the circuit has an optimal magnetizing inductance such that the AC voltage and current signals received at the primary side of the transformer are substantially in phase with each other, thereby substantially reducing or eliminating the reactive power transferred by the transformer.
- the magnetizing inductance, L m is given as:
- ⁇ s is an operating frequency
- C 1 is the capacitance of the capacitor
- R 1 is the resistance of the at least one lamp
- n is a secondary-to-primary side turns ratio of the transformer.
- FIG. 1 is a schematic diagram of a prior art lamp ballast circuit
- FIG. 2 is a phasor diagram for a prior art lamp ballast circuit
- FIG. 3 is a schematic diagram of a lamp ballast circuit in accordance with one embodiment of the invention.
- FIG. 4 is a phasor diagram for a lamp ballast circuit, in accordance with one embodiment of the present invention.
- the present invention in accordance with one embodiment, is a lamp ballast circuit which adjusts the magnetizing inductance of a lamp ballast circuit transformer.
- the magnetizing inductance of the transformer By optimizing the magnetizing inductance of the transformer, the voltage and current signals received by the transformer are brought into phase relative to each other, and the reactive power transferred through the output transformer is substantially reduced or eliminated.
- FIG. 2 is a phasor diagram which employs vectors to illustrate the reactive power required to be provided by transformer 110 of FIG. 1 .
- FIG. 2 shows that vector I p , which represents the current supplied to transformer 110 , is ⁇ degrees out of phase with V p , which represents the voltage supplied to transformer 110 .
- the magnetizing current of the circuit, represented by the vector I m is supplied by transformer 110 when necessary to balance the lamp load.
- FIG. 3 is a circuit diagram that illustrates the salient features of a lamp ballast circuit 10 , in accordance with one embodiment of the present invention.
- the circuit shown in FIG. 3 is suitable to be used in the ballast of a fluorescent lamp.
- the present invention is not intended to be limited in scope in this regard, as it is suitable to be employed in other ballast designs, such as LCD backlighting.
- FIG. 3 illustrates a circuit that is an equivalent design of that shown in FIG. 1 .
- the AC sinusoidal supply source 22 is a schematic representation of and is equivalent to the part of the circuit shown in FIG. 1 that is coupled to the primary side 110 a of the transformer 110 .
- FIG. 3 simplifies the illustration of the output stage of the circuit shown in FIG. 1 .
- the voltage across the resonant capacitor 116 is substantially sinusoidal and is shown therein as vector V p .
- FIG. 3 shows vector V p , which illustrates the voltage which may exist across a resonant capacitor (not shown in FIG. 3) and which is again substantially sinusoidal.
- FIG. 3 also shows a transformer 12 , which comprises a primary winding 14 and a secondary winding 16 . Coupled in parallel across primary winding 14 is magnetizing inductor 24 , which is further explained below.
- circuit 10 comprises a lamp 20 in series with a capacitor 18 .
- parallel-connected lamps such as those illustrated in, FIG. 1 are combined into a single equivalent lamp 20 for the sake of simplicity.
- lamp resistance R 1 of lamp 20 is the resistance of a single lamp or else is equivalent to the combined resistance of several parallel-connected lamps.
- the parallel-connected capacitors such as those illustrated in FIG. 1, are combined into a single capacitor 18 coupled in series with lamp 20 .
- capacitance C 1 of capacitor 20 is the capacitance of a single capacitor or else is equivalent to the combined capacitance of several parallel-combined capacitors.
- the magnetizing inductance of magnetizing inductor 24 is configured so that the voltage and current received by primary winding 110 a of transformer 110 are in phase relative to each other.
- transformer 110 does not transfer any reactive power.
- the additional energy i.e.—the reactive power
- the reactive power which would typically be required to be supplied by the circuit in order to balance the load is compensated by the magnetizing inductance of magnetizing inductor 24 .
- FIG. 4 is a phasor diagram which employs vectors to illustrate the advantage of the present invention.
- reactive power required to balance the load is provided by magnetizing inductor 24 of transformer 110 .
- the phasor diagram of FIG. 4 shows an increase of vector I m .
- Vector I m represents the magnetizing current through magnetizing inductor 24 .
- the current I p provided to transformer 12 is brought into phase with the voltage V p at transformer 12 . This is shown in FIG. 4, wherein the angle ⁇ between vector I p and vector V p is substantially zero. At this point, the current I p is also reduced. It is noted that in accordance with one embodiment of the invention, with the increasing magnetizing current I m , there is a point when I p reaches its substantially minimal value, at which V p and I p are in phase relative to each other.
- the optimal value of the magnetizing inductance L m can be determined for a given operating frequency ⁇ s as:
- C 1 is the capacitance of capacitor 18 (or the equivalent capacitance of more than one parallel-connected capacitors)
- R 1 is the resistance of the lamps (or the equivalent resistance of more than one parallel-connected lamps)
- n is the secondary-to-primary side turns ratio of transformer 12 .
- the magnetizing inductance L m When the magnetizing inductance L m , is optimized at this value, the reactive power which is typically transferred through the transformer is substantially eliminated. As a result, the size of the transformer may be significantly smaller, since the transformer is no longer required to transfer a significant amount of reactive power. Thus, the inclusion of magnetizing inductor 24 insures that the reactive power is always sufficient to balance the load. It is noted, however, that the present invention also contemplates that, instead of employing a magnetizing inductor 24 as shown in FIG. 3, a transformer is employed in which the primary-to-secondary side turns ratio of the transformer provides for the optimal magnetizing inductance as defined by Equation 1 above.
Abstract
Description
Claims (28)
Priority Applications (1)
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US09/580,170 US6407935B1 (en) | 2000-05-30 | 2000-05-30 | High frequency electronic ballast with reactive power compensation |
Applications Claiming Priority (1)
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US09/580,170 US6407935B1 (en) | 2000-05-30 | 2000-05-30 | High frequency electronic ballast with reactive power compensation |
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US6407935B1 true US6407935B1 (en) | 2002-06-18 |
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US09/580,170 Expired - Lifetime US6407935B1 (en) | 2000-05-30 | 2000-05-30 | High frequency electronic ballast with reactive power compensation |
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Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060022617A1 (en) * | 2004-08-02 | 2006-02-02 | Chunghwa Picture Tubes, Ltd. | Backlight module for reducing interference |
EP1814367A1 (en) * | 2004-11-12 | 2007-08-01 | Minebea Co., Ltd. | Backlight inverter and its driving method |
US20140333205A1 (en) * | 2013-05-13 | 2014-11-13 | Cirrus Logic, Inc. | Stabilization circuit for low-voltage lighting |
US9167664B2 (en) | 2012-07-03 | 2015-10-20 | Cirrus Logic, Inc. | Systems and methods for low-power lamp compatibility with a trailing-edge dimmer and an electronic transformer |
US9215765B1 (en) | 2012-10-26 | 2015-12-15 | Philips International, B.V. | Systems and methods for low-power lamp compatibility with an electronic transformer |
US9215770B2 (en) | 2012-07-03 | 2015-12-15 | Philips International, B.V. | Systems and methods for low-power lamp compatibility with a trailing-edge dimmer and an electronic transformer |
US9263964B1 (en) | 2013-03-14 | 2016-02-16 | Philips International, B.V. | Systems and methods for low-power lamp compatibility with an electronic transformer |
US9273858B2 (en) | 2012-12-13 | 2016-03-01 | Phillips International, B.V. | Systems and methods for low-power lamp compatibility with a leading-edge dimmer and an electronic transformer |
US9385598B2 (en) | 2014-06-12 | 2016-07-05 | Koninklijke Philips N.V. | Boost converter stage switch controller |
US9635723B2 (en) | 2013-08-30 | 2017-04-25 | Philips Lighting Holding B.V. | Systems and methods for low-power lamp compatibility with a trailing-edge dimmer and an electronic transformer |
Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5332951A (en) | 1992-10-30 | 1994-07-26 | Motorola Lighting, Inc. | Circuit for driving gas discharge lamps having protection against diode operation of the lamps |
US5539630A (en) * | 1993-11-15 | 1996-07-23 | California Institute Of Technology | Soft-switching converter DC-to-DC isolated with voltage bidirectional switches on the secondary side of an isolation transformer |
US5781418A (en) | 1996-12-23 | 1998-07-14 | Philips Electronics North America Corporation | Switching scheme for power supply having a voltage-fed inverter |
US5808879A (en) * | 1996-12-26 | 1998-09-15 | Philips Electronics North America Corporatin | Half-bridge zero-voltage-switched PWM flyback DC/DC converter |
US5838558A (en) * | 1997-05-19 | 1998-11-17 | Trw Inc. | Phase staggered full-bridge converter with soft-PWM switching |
US5907223A (en) * | 1995-12-08 | 1999-05-25 | Philips Electronics North America Corporation | Two-frequency electronic ballast system having an isolated PFC converter |
US5999433A (en) * | 1998-01-12 | 1999-12-07 | Vpt, Inc. | Half-bridge DC to DC converter with low output current ripple |
US6072710A (en) * | 1998-12-28 | 2000-06-06 | Philips Electronics North America Corporation | Regulated self-oscillating resonant converter with current feedback |
US6088250A (en) * | 1998-05-29 | 2000-07-11 | The Aerospace Corporation | Power converters for multiple input power supplies |
US6181079B1 (en) * | 1999-12-20 | 2001-01-30 | Philips Electronics North America Corporation | High power electronic ballast with an integrated magnetic component |
-
2000
- 2000-05-30 US US09/580,170 patent/US6407935B1/en not_active Expired - Lifetime
Patent Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5332951A (en) | 1992-10-30 | 1994-07-26 | Motorola Lighting, Inc. | Circuit for driving gas discharge lamps having protection against diode operation of the lamps |
US5539630A (en) * | 1993-11-15 | 1996-07-23 | California Institute Of Technology | Soft-switching converter DC-to-DC isolated with voltage bidirectional switches on the secondary side of an isolation transformer |
US5907223A (en) * | 1995-12-08 | 1999-05-25 | Philips Electronics North America Corporation | Two-frequency electronic ballast system having an isolated PFC converter |
US5781418A (en) | 1996-12-23 | 1998-07-14 | Philips Electronics North America Corporation | Switching scheme for power supply having a voltage-fed inverter |
US5808879A (en) * | 1996-12-26 | 1998-09-15 | Philips Electronics North America Corporatin | Half-bridge zero-voltage-switched PWM flyback DC/DC converter |
US5838558A (en) * | 1997-05-19 | 1998-11-17 | Trw Inc. | Phase staggered full-bridge converter with soft-PWM switching |
US5999433A (en) * | 1998-01-12 | 1999-12-07 | Vpt, Inc. | Half-bridge DC to DC converter with low output current ripple |
US6088250A (en) * | 1998-05-29 | 2000-07-11 | The Aerospace Corporation | Power converters for multiple input power supplies |
US6072710A (en) * | 1998-12-28 | 2000-06-06 | Philips Electronics North America Corporation | Regulated self-oscillating resonant converter with current feedback |
US6181079B1 (en) * | 1999-12-20 | 2001-01-30 | Philips Electronics North America Corporation | High power electronic ballast with an integrated magnetic component |
Cited By (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7106010B2 (en) * | 2004-08-02 | 2006-09-12 | Chunghwa Picture Tubes, Ltd. | Backlight module for reducing interference |
US20060022617A1 (en) * | 2004-08-02 | 2006-02-02 | Chunghwa Picture Tubes, Ltd. | Backlight module for reducing interference |
EP1814367A1 (en) * | 2004-11-12 | 2007-08-01 | Minebea Co., Ltd. | Backlight inverter and its driving method |
EP1814367A4 (en) * | 2004-11-12 | 2009-04-08 | Minebea Co Ltd | Backlight inverter and its driving method |
US9655202B2 (en) | 2012-07-03 | 2017-05-16 | Philips Lighting Holding B.V. | Systems and methods for low-power lamp compatibility with a leading-edge dimmer and a magnetic transformer |
US9167664B2 (en) | 2012-07-03 | 2015-10-20 | Cirrus Logic, Inc. | Systems and methods for low-power lamp compatibility with a trailing-edge dimmer and an electronic transformer |
US9215770B2 (en) | 2012-07-03 | 2015-12-15 | Philips International, B.V. | Systems and methods for low-power lamp compatibility with a trailing-edge dimmer and an electronic transformer |
US9215765B1 (en) | 2012-10-26 | 2015-12-15 | Philips International, B.V. | Systems and methods for low-power lamp compatibility with an electronic transformer |
US9277624B1 (en) | 2012-10-26 | 2016-03-01 | Philips International, B.V. | Systems and methods for low-power lamp compatibility with an electronic transformer |
US9273858B2 (en) | 2012-12-13 | 2016-03-01 | Phillips International, B.V. | Systems and methods for low-power lamp compatibility with a leading-edge dimmer and an electronic transformer |
US9341358B2 (en) | 2012-12-13 | 2016-05-17 | Koninklijke Philips N.V. | Systems and methods for controlling a power controller |
US9263964B1 (en) | 2013-03-14 | 2016-02-16 | Philips International, B.V. | Systems and methods for low-power lamp compatibility with an electronic transformer |
US20140333205A1 (en) * | 2013-05-13 | 2014-11-13 | Cirrus Logic, Inc. | Stabilization circuit for low-voltage lighting |
US9385621B2 (en) * | 2013-05-13 | 2016-07-05 | Koninklijke Philips N.V. | Stabilization circuit for low-voltage lighting |
US9635723B2 (en) | 2013-08-30 | 2017-04-25 | Philips Lighting Holding B.V. | Systems and methods for low-power lamp compatibility with a trailing-edge dimmer and an electronic transformer |
US9385598B2 (en) | 2014-06-12 | 2016-07-05 | Koninklijke Philips N.V. | Boost converter stage switch controller |
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